Various devices can be installed in a well traversing a hydrocarbon-bearing subterranean formation. Some devices control the flow rate of fluid between the formation and tubing, such as production or injection tubing. An example of these devices is an autonomous valve that can select fluid, or otherwise control the flow rate of various fluids into the tubing.
An autonomous valve can select between desired and undesired fluids based on relative viscosity of the fluids. For example, fluid having a higher concentration of undesired fluids (e.g. water and natural gas) may have a certain viscosity in response to which the autonomous valve directs the undesired fluid in a direction to restrict the flow rate of the undesired fluid into tubing. The autonomous valve may include a switching mechanism that is, for example, in a flow ratio control device and may include a vortex assembly usable to select fluid based on viscosity. The flow ratio control assembly can include two passageways. Each passageway can include narrowed tubes that are configured to restrict fluid flow based on viscosity of the fluid. For example, one tube in the first passageway may be narrower than the second tube in the second passageway, and configured to restrict fluid having a certain relative viscosity more than fluid having a different relative viscosity. The second tube may offer relatively constant resistance to fluid, regardless of the viscosity of the fluid.
Fluid entering the vortex assembly via a first passageway, such as a passageway that is tangential to the vortex assembly, may be caused to rotate in the vortex assembly and restricted from exiting an exit opening in the vortex assembly. Fluid entering the vortex assembly via a second passageway, such as a passageway that is radial to the vortex assembly, may be allowed to exit through the exit opening without any, or much, restriction.
Although this autonomous valve is very effective in meeting desired fluid selection downhole, devices that can facilitate greater fluid switching are desirable.